Thermostats in refrigerators and freezers control temperature by switching cooling on and off. In older or simpler models, a mechanical thermostat directly turns the compressor on/off based on a capillary sensor. In many modern appliances, an electronic thermostat function is handled by temperature sensors (NTC) plus the control board, which regulates the compressor, fans, and dampers more precisely.

Common problems include:

• Too warm: thermostat not calling for cooling, bad sensor, poor airflow, or a control issue.

• Too cold / food freezing: thermostat contacts stuck closed, sensor reading wrong, or damper stuck open.

• Compressor runs nonstop: thermostat/sensor error, dirty condenser, weak sealing, or a sealed-system problem.

• Frequent cycling: incorrect sensor values, poor ventilation, or control board instability.

Basic steps: confirm the set temperature, don’t block air vents, clean the condenser, and check the door gasket. Diagnosing a thermostat or sensor typically requires measuring continuity/resistance and should be done with the appliance unplugged, if the model uses a control board, correct part matching is important.